How to display properties when selected from enum
Include an if-then statement in your draw function, like this:

import bpy
from bpy.props import IntProperty, FloatProperty, EnumProperty


def initSceneProperties(scn):
    bpy.types.Scene.MyInt = IntProperty(
        name = "Integer", 
        description = "Enter an integer")
    scn['MyInt'] = 17

    bpy.types.Scene.MyFloat = FloatProperty(
        name = "Float", 
        description = "Enter a float",
        default = 33.33,
        min = -100,
        max = 100)

    bpy.types.Scene.MyEnum = EnumProperty(
        items = [('Eine', 'Flash', 'One'), 
                 ('Zwei', 'Fountain', 'Two'),
                 ('Drei', 'Split', 'Three')],
        name = "Manuevers")
    scn['MyEnum'] = 2

    bpy.types.Scene.FlashDistance = FloatProperty(
        name="Flash Distance",
        min=1.0,
        default=1.0)

    return

initSceneProperties(bpy.context.scene)

#
#    Menu in UI region
#

class UIPanel(bpy.types.Panel):
    bl_label = "Property panel"
    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"

    def draw(self, context):
        layout = self.layout
        scn = context.scene

        layout.prop(scn, 'MyInt', icon='BLENDER', toggle=True)
        layout.prop(scn, 'MyFloat')

        layout.prop(scn, 'MyEnum')
        row = layout.row()
        row.enabled = False

        if scn.MyEnum == "Eine":
            layout.prop(scn, 'FlashDistance')

        layout.operator("idname_must.be_all_lowercase_and_contain_one_dot")

#
#    The button prints the values of the properites in the console.
#

class OBJECT_OT_PrintPropsButton(bpy.types.Operator):
    bl_idname = "idname_must.be_all_lowercase_and_contain_one_dot"
    bl_label = "Print props"

    def execute(self, context):
        scn = context.scene

        printProp("Int:    ", 'MyInt', scn)
        printProp("Float:  ", 'MyFloat', scn)
        printProp("Enum:   ", 'MyEnum', scn)


        return{'FINISHED'}    

def printProp(label, key, scn):
    try:
        val = scn[key]
    except:
        val = 'Undefined'
    print("%s %s" % (key, val))



bpy.utils.register_module(__name__)